Various types of carpet cleaning machines have been produced over the past several years which typically may be rented for use in the home or they may be operated by a professional carpet cleaner. The designs of such machines are based on one or more cleaning methods.
The most commonly used method of cleaning carpets has been by shampooing. This method usually consists of applying a soapy or detergent-based foam to the surface of the carpet and brushing it in with a powered brush. The carpet is then left to stand for a period of time ranging from a few hours to a day before the dried foam and entrapped soil is removed by vacuuming. Shampooing in this manner is effective in removing surface soil and stains, but it has little or no effect in removing embedded dirt and sand. Furthermore, after a carpet has been shampooed several times, it reaches a state wherein the buildup of residue from the shampoo itself is so great that this method is no longer effective.
Another method of cleaning carpets involves the discharging of pressurized "steam" (actually hot water) into the carpet and, in the same operation, removing the hot water by vacuum along with the entrained dust and dirt. This method is effective in removing deeply embedded soil, but it is only marginally effective in removing stains.
Frequently a professional carpet-cleaner will own two machines including a foam cleaner and a hot water or "steam" cleaner, and he will utilize one or both methods to clean a carpet, depending upon the condition of the carpet.
Numerous machine designs of both types are described in the prior art. Machines cleaning strictly by means of foam or shampoo are disclosed by R. R. Rockwell (U.S. Pat. No. 3,079,285), J. Wright (U.S. Pat. No. 3,364,627), L. G. Schowalter (U.S. Pat. No. 3,392,418), and Nayfa et al (U.S. Pat. No. 4,000,537). Steam or hot water carpet cleaning machines are disclosed by J. O. Jones (U.S. Pat. No. 3,614,797), Putt (U.S. Pat. No. 3,699,607), Cannan (U.S. Pat. No. 3,919,729), Cyphert (U.S. Pat. No. 3,959,844), and Silvis et al (U.S. Pat. No. 3,974,541).
In the prior art machines of both types there are such common features as motors, self-propelling drives, supporting frames, wheels, etc. for which a professional carpet cleaner must pay twice if he owns both types of machines, but because there has been no universal cleaning machines available which incorporates both cleaning methods, he has no alternative.
There is, therefore, a need for a carpet-cleaning machine which provides both cleaning methods on a single frame so that a greater degree of versatility may be provided at a lower equipment cost.